The main problem with Chomsky's approach is that it is quite likely that human intelligence mechanics are just incomprehensible for a human intelligence, and not because of some crazy construction tricks but simply plain old brute size and complexity it imposes. Judging from much simpler (thus deeper investigated) biological systems like some bacteria metabolisms we can see that there is no grand design there, only trivial primitive core and numerous layers of less or more subtle modifiers of modifiers. IMO there is no reason why the same can't work for the brain and thus the "transition to sentience" is way more continuous than we would like to expect.